P1340: MONOCYTE-DRIVEN INFLAMMATION IN DNMT3A-MUTANT CLONAL HAEMATOPOIESIS ACUTE ST-ELEVATION MYOCARDIAL INFARCTION.
Authors: Sarah Mackie, Matthew Sadler, Douglas Silveira, Hosanna Assefa-Kebede, Pilar Casares Alaez, Giorgio Napolitani, Aleksander Ivetic, Daniel Bromage, Lynn Quek
Journal: HemaSphere (2023)

Topic: 23. Hematopoiesis, stem cells and microenvironment Background: In clonal haematopoiesis of indeterminate potential (CHIP), haematopoietic stem cells acquire mutations and produce mutant blood cells without overt blood disease. CHIP is a novel independent risk factor in ischaemic heart disease and heart failure (HF)1. Myocardial infarction (MI) is a leading cause of HF due to scar formation and ventricular remodelling. We postulate that CHIP mutations cause aberrant inflammation but the molecular mechanisms are poorly understood. We investigated clinical outcomes and immune cell biology in CHIP and non-CHIP patients (pts) with acute ST-segment elevation MI (STEMI). Aims: 1.Identify mutations variant allele frequency (VAF) ≥ 1% in STEMI pts 2.Assess leukocyte mutational 3.Investigate transcription profiles and leukocyte effector function in CHIP and non-CHIP STEMI pts Methods: 91 pts diagnosed with STEMI were prospectively recruited (REC 19/SC/0362). We collected clinical data, including echocardiogram (Echo) parameters during index admission and post-STEMI, and isolated plasma and peripheral blood mononucleated cells (PBMCs) from blood collected 48-96 hours post onset of chest pain. PBMCs were screened for mutations and analysed by flow cytometry. In CHIP pts, we assessed VAF with digital droplet PCR in flow-sorted monocytes (Mono), T and B-cells. We performed single-cell RNAseq (10x Genomics) on sorted leukocytes from CHIP and non-CHIP pts. Results: 78 pts had an Echo during admission, 55 had follow-up Echo at median 5.7 (IQR 2.6-15.3) months post-STEMI. 50% had ≥ 1 CHIP mutation (VAF 1-22%). DNMT3A was the most commonly mutated gene (31.4%), followed by TET2 (14.3%) and ASXL1 (5.7%). While baseline LV ejection fraction (LVEF) was similar in CHIP and non-CHIP pts, we saw a trend towards reduced LVEF recovery post-STEMI (p=0.07) in DNMT3A versus non-CHIP pts, and no difference between non-DNMT3A CHIP and non-CHIP pts. CHIP mutation VAFs were highest in Mono (mean VAF 6.3%), present in B cells (3%), but rare in T cells (1.65%). DNMT3A-mutant pts had more classical Mono (CM) compared to non-CHIP (91% vs. 80% of total Mono, p=0.0285). Non-DNMT3A CHIP pts had the same trend of more CM compared to non-CHIP (87% vs. 80% p=0.18). Average VAF for Mono in DNMT3A CHIP samples was 6.43%. Using scRNAseq, we computed Mono trajectories and differential gene expression. Compared to non-CHIP, pathways upregulated in Mono from DNMT3A-mutant samples were receptor for advanced glycation end-products (RAGE) and toll-like receptor signalling (associated with damage-associated molecular pattern pathway), while antigen presentation and interferon response were downregulated. Upregulation of innate inflammatory pathways were observed in lymphoid populations, suggesting that these could be driven by cell-cell/paracrine signalling. Deep immune cell profiling by mass-cytometry and cytokine profiling of plasma are underway. Summary/Conclusion: Our novel findings are: 1.A trend towards impaired LVEF recovery post-STEMI in DNMT3A CHIP pts 2.Enrichment of CHIP mutations in Mono, with significant clonal involvement of B- but not of T-cells, which has not been previously described in STEMI pts 3.Heightened pro-inflammatory signalling in Mono in DNMT3A CHIP pts which is likely to involve cross-talk with lymphoid populations. DNMT3A CHIP is associated with a pro-inflammatory phenotype that could adversely affect cardiac remodelling and negatively impact patient recovery. 1. Jaiswal et al. NEJM2017 Keywords: Inflammation, Myocardial infarction, Clonal hematopoiesis of indeterminate potential